Laser machining apparatus

ABSTRACT

This invention relates to improvement in a laser machining apparatus using both a working laser generator (101) and an auxiliary energy supplying apparatus (110) such as a plasma or the like. A feature of the invention is that an auxiliary energy generated from the auxiliary energy supplying apparatus is radiated on a workpiece (118) to a location which is slightly apart from an irradiation point of a working laser beam. In a preferred embodiment, the auxiliary energy supplying apparatus (110) is attached to a rotary disk (113) thereby allowing the auxiliary energy to be radiated to a location which is always preceding an irradiation point of the laser beam in the working progressing direction. The auxiliary energy may be radiated onto a surface opposite to the surface of a workpiece to which the laser beam is radiated. With such an arrangement, working efficiency and accuracy are improved and a structure of the whole system is also simplified, resulting in less failure. To further improve the working efficiency, in a desirable embodiment, an abrasive grain may be supplied to the working portion, or a high-pressure working fluid may be jetted thereto, or a working fluid to which an ultrasonic vibrational energy was applied may be supplied thereto. Further, a focal point automatic adjusting mechanism of the laser beam may be provided.

FIELD OF THE INVENTION

The present invention relates to a laser machining apparatus and, moreparticularly, to improvements in a laser machining apparatus which worksby applying both a laser beam as a main energy source for the workingoperation and an auxiliary energy source of plasma or the like.

BACKGROUND OF THE INVENTION

A laser machining apparatus in which a laser beam is focused by afocusing lens and performs the working operation while radiating thelaser beam onto a workpiece is publicly known and is widely utilized.Further, a laser machining apparatus which works using both the laserbeam and another auxiliary energy source such as a plasma jet or thelike and thereby improving the working efficiency has been developed andis being used.

In the above-mentioned laser machining apparatus, although the workingefficiency and working speed were remarkably improved as compared withconventional laser machining apparatus, the working efficiency and speedare still low and, particularly, in the case of cutting and working athick workpiece or the like, it takes a long time and a high degree ofworking accuracy cannot be obtained.

Such a conventional laser machining apparatus using an auxiliary energysource performs the working by collecting the laser and the auxiliaryenergy onto the same irradiation point on a workpiece. When giving arelative movement between the workpiece and the irradiation point of theworking laser beam and thereby performing the cutting work or weldingwork, etc., there is the problem that the heating by the auxiliaryenergy is not effectively utilized to the best advantage for the workingby the laser beam.

In addition, in the case of working by collecting the working laser beamand the auxiliary energy onto the same irradiation point on a workpiece,the lens system for focusing the laser beam and the means for generatingthe auxiliary energy overlap at a certain portion, such that thearrangement of the apparatus becomes complicated and also its operationbecomes troublesome.

On the other hand, although the auxiliary energy is provided to mainlyheat a workpiece to a constant temperature and thereby to assist theworking by the laser beam, since a portion of constant extent is heatedby the irradiation of the auxiliary energy, in the case where theworkpiece is relatively moving for the irradiation point of the workinglaser beam, a rear portion in the progressing direction of the workingwhere the auxiliary energy is irradiated reaches a higher temperaturethan the front portion thereof. This is inconvenient since it results inwasted consumption of energy and causes distortion.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a laser machiningapparatus which can work a workpiece in a short time and can perform theworking with a high degree of accuracy and with extremely high workingefficiency and also high working speed by use of an auxiliary energysource as effectively as possible even in the case where a particularlythick workpiece is to be worked.

The gist of the invention is as follows. In a laser machining apparatuswhich allows a laser beam from a laser generator to be focused by afocusing lens and works a workpiece while radiating the laser beamthereon, a plasma generating apparatus or other auxiliary energy sourcesis provided, and at the same time the radiating portion of the laserbeam onto the workpiece and the radiating position of the auxiliaryenergy are slightly shifted. Preferably, the auxiliary energy is alwaysradiated onto the portion which precedes the irradiation point of theworking laser beam in the progressing direction of the work. In the casewhere the workpiece is a relatively thin material, the laser beam andauxiliary energy may be respectively radiated onto opposite sides of theworkpiece. With such an arrangement, there is provided a laser machiningapparatus with simple arrangement and with less failure in which theauxiliary energy can be utilized effectively and the apparatus can beeasily handled.

As an auxiliary energy source, a plasma, Xenon light, glow discharge,corona discharge, or an auxiliary laser beam or the like are useful.

The case of using a plasma jet as an auxiliary energy source, theexhausted gas from the laser generator can be utilized as a part of theplasma gas.

In several desirable embodiments of the laser machining apparatusaccording to the present invention as mentioned above, varioussupplementary means can be also used in order to allow the working bythe laser beam and auxiliary energy to be performed further efficiently.Namely, a working fluid such as water, acid, alkali, or the like issupplied as a high-pressure jet to the portion on the workpiece wherethe laser beam is radiated, thereby facilitating the working. Also aworking fluid such as acid, alkali or the like is supplied to theportion to be worked, and at the same time 80% or more of the workingfluid is evaporated by the working laser beam, thereby performing theworking efficiently. Further, the working fluid can be subjected toultrasonic vibrational energy and supplied to the working portion or theportion immediately after completion of the working. Additionally anabrasive grain can be discharged against the working portion.Furthermore, the working can be performed in an atmosphere of halogengas. Moreover, in order to automatically adjust the focal point of thelaser beam, it is also possible to provide means for sensing infraredrays radiated from the working portion, thereby adjusting the positionof the focal point so that the quantity of the infrared radiationbecomes maximum. It is also possible to provide means for radiating asighting light toward the workpiece, thereby automatically adjusting theposition of the focal point of the laser beam by use of the sightinglight reflected from the workpiece.

The above objects, arrangements, functions, and effects of the presentinvention will be more apparent from the following detailed descriptionin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing one embodiment of a laser machiningapparatus according to the present invention in which a plasma is usedas auxiliary energy and the plasma is radiated onto a portion of aworkpiece which is precedent from the position where a working laserbeam is radiated;

FIG. 2 is a diagram showing the positional relation between theirradiation point of the working laser beam and the position where theplasma is radiated in the laser machining apparatus according to thepresent invention shown in FIG. 1;

FIG. 3 is a diagram showing one embodiment in which a plasma asauxiliary energy is radiated onto a workpiece from the side opposite tothe working laser beam;

FIG. 4 is a diagram showing one embodiment in which a laser beam asauxiliary energy is radiated onto a workpiece from the side opposite tothe working laser beam;

FIG. 5 is a diagram showing one embodiment in which a glow or coronadischarge as auxiliary energy is radiated onto the portion around theworking laser beam;

FIG. 6 is a diagram showing one embodiment in which a glow or coronadischarge as auxiliary energy is radiated onto the portion around theworking laser beam and at the same time abrasive grain is spouted towardthe working portion;

FIG. 7 is a diagram showing one embodiment in which a Xenon light isused as auxiliary energy and a plasma gas and a high-pressure fluid aresupplied to the working portion;

FIG. 8 is a diagram showing one embodiment in which an exhaust gas fromthe working laser generator is used as a part of a plasma gas togenerate a plasma as auxiliary energy;

FIG. 9 is a diagram showing one embodiment in which a plasma is used asauxiliary energy and a working fluid is supplied to the working portion,and at the same time 80% or more of the working fluid is evaporatedthereby carrying out the working;

FIG. 10 is a diagram showing one embodiment in which a plasma is used asauxiliary energy and the plasma is radiated onto the position of aworkpiece which is precedent from the position where the working laserbeam is radiated, and at the same time a working fluid to which theultrasonic energy was applied is supplied to the working portion or theportion immediately after completion of the working, thereby carryingout the working;

FIG. 11 is a diagram showing one embodiment in which a plasma is used asauxiliary energy and infrared rays from the working portion is sensed,thereby automatically controlling the position of the focal point of thelaser beam;

FIG. 12 is a diagram showing one embodiment in which a plasma is used asauxiliary energy and a light source for sighting is also equipped,thereby automatically controlling the position of the focal point of thelaser beam; and

FIG. 13 is a diagram showing the details of a photoelectric converterwhich is provided in the apparatus shown in FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates one embodiment of a laser machining apparatus inwhich a plasma jet as auxiliary energy source is radiated onto aposition of a workpiece which precedes the position where a workinglaser beam is radiated in the working progressing direction according tothe present invention.

In FIG. 1, reference numeral 101 denotes a laser generator; 102 is areflection mirror; 103 a member to attach the reflecting mirror; 104 apiping system for cooling; 105 a refrigerant supplying apparatus tosupply cooling water or the like; 106 a focusing lens; 107 a member tofix the lens; 108 a housing; 109 a working gas supply port; 110 a plasmagun; 111 a plasma gas supply tube; 112 a member to attach the plasmagun; 113 a rotary disk; 114 a rotary disk attaching base; 115 a crowngear; 116 a pinion gear; 117, 123 and 124 motors; 118 a workpiece; 119 across slide table; 120 a traveling table in the direction of the X axis;121 a traveling table in the direction of the Y axis; 122 a base; and125 a numerical control unit.

In the embodiment, a plasma generating apparatus was used as anauxiliary energy supplying apparatus; however, in place of this, it isalso possible to use a discharging apparatus such as an arc discharge,high-frequency pulse discharge or the like, or a laser generatordifferent from the working laser generator.

For the laser generator 101, it is possible to use any gas laser such asa C0₂ laser, He-Ne laser, etc., a liquid laser, a solid state laser suchas a ruby laser, YAG laser, etc., or a semiconductor laser. The power ofsuch a laser generator can be increased by means of a pulsatingoscillation using a Q-switching method. On the other hand, the magnitudeof energy density of the laser beam is controlled by a control unit (notshown) connected to the laser generator 101.

The reflecting mirror 102 is attached to the mirror attaching member 103fixed to the housing 108 and is constituted such that it has an angle of45° to the optical axis of the laser beam generated from the lasergenerator 101, thereby allowing the optical path of the laser beam to bechanged by an angle of 90°.

The piping system 104 for cooling is arranged such that it passesthrough the mirror attaching member 103 and cooling water is suppliedthrough the piping system 104 by the refrigerant supplying apparatus105, thereby cooling the reflecting mirror 102 and the attaching member103.

The housing 108 is a hollow box and is constituted in the manner suchthat the central axis of the cylindrical pipe at its central portioncoincides with the optical axis of the laser beam reflected by thereflecting mirror 102. One end of the housing 108 is formed like atapered shape and a working gas exhausting nozzle 108a is provided atthe end.

The laser beam reflected by the reflecting mirror 102 is focused by thelens 106 and is converged to a working point on the workpiece 118.

The lens fixing member 107 is positioned and attached to the housing 108such that the focal point of the lens 106 coincides with the workingpoint on the workpiece 118.

In the arrangement in which the position of the housing 108 is fixed tothe workpiece 118, the lens 106 may be necessary to be controlled andmoved along the optical axis of the laser beam in response to aprogrammed command or the like. However, in general, the housing 108 orcross slide table 119 are controlled to be moved away or towards eachother and the converged focal point of the laser beam in the directionof a thickness of the workpiece 118 to be worked can be changed.

In addition, the lens 106 and lens fixing member 107 also serve aspressure resistant members to seal the working gas which is suppliedinto the housing 108.

A working, i.e., a halogen, furon of various kinds, water vapor, oxygen,inert gases, carbon dioxide, or mixtures of these gases is suppliedthrough the working gas supply port 109 into the housing 108 inaccordance with the kind of workpiece 118. These gases areconcentratedly discharged from the gas exhausting nozzle 108a of thehousing 108 to the irradiation point of the laser beam.

By discharging the working gas to the irradiation point of the laserbeam, the working by the main working laser is carried out effectively,and at the same time the extent of the round edge in the cross sectionis reduced; furthermore, it becomes possible to drain the working debrisrapidly.

A plasma gas is supplied from the gas supply tube 111 to the plasma gun110, and a voltage is applied thereto by a plasma power source (notshown), so that the plasma gun generates a plasma. The plasma jet gun isattached to the rotary disk 113 with the attaching member 112 in themanner such that the radiating direction of the plasma jet has an angleof 20° to 50° relative to the optical axis of the laser beam.

In addition, the magnitude of energy density of the plasma jet can bechanged by controlling the plasma power source apparatus (not shown).

The rotary disk 113 is annular so as to surround the outer periphery ofthe housing 108 and is rotatably mounted on the attaching base 114 fixedto the housing 108.

The crown gear 115 engages the pinion gear 116 fixed to an axis of themotor 117 and is fixed to the rotary disk 113 coaxially, so that it isrotated integrally therewith.

With such an arrangement, the plasma gun 110 is rotated integrally withthe rotary disk 113 around the optical axis of the working laser beam,so that the radiating position of the plasma jet can be coaxiallyrotated around the irradiation point of the main laser beam and itsrotational angle can be set to an arbitrary value of 0° to 360° .

The workpiece 118 is attached to the traveling table 120 which ismovable along the X axis of the cross slide table 119. The travelingtable 120 is movable along the X axis and the traveling table 121 alongthe Y-axis by the motors 123 and 124. Thus, the workpiece 118 is movedtwo-dimensionally in the same plane.

In accordance with a predetermined program, the numerical control unit125 controls the motors 123 and 124, thereby allowing the workpiece 118attached to the cross slide table 119 to be moved in desired positionand direction at a predetermined speed. At the same time, in accordancewith the working progressing direction which is determined by signalssent to the motors 123 and 124, the control unit 125 makes the motor 117operative for allowing the rotary disk 113 to be properly rotated, suchthat the radiating position of the plasma jet is always head in theworking progressing direction of the irradiation point of the workinglaser beam.

The working laser beam generated from the laser generator 101 isreflected by the reflecting mirror 102 and its optical path is changed,thereafter it is focused by the lens 106 and is converged onto theworking point on the workpiece 118.

On the other hand, the plasma gun 110 is constituted such that it isrotated integrally with the rotary disk 113 and can be set to anarbitrary position. The numerical control unit 125 controls the motors123 and 124 and determines the working progressing direction of theworkpiece 118, and at the same time it controls the motor 117 incorrespondence to the working progressing direction to rotate the rotarydisk 113, such that the position of the plasma gun 110 attached to therotary disk 113 is always precedent in the working progressing directionfor the irradiation point of the working laser beam. Therefore, theplasma generated from the plasma gun 110 is always irradiated on theprecedent portion in the working progressing direction for theirradiation point of the working laser beam.

FIG. 2 is an explanatory diagram showing the positional relationshipbetween the radiating position of the plasma jet and the irradiationpoint of the working laser beam.

In the diagram, numeral 226 denotes a portion onto which the plasma isradiated and 227 indicates a point at the highest temperature.

In the preferred embodiment, as shown in the diagram, the portion 226where the plasma jet is radiated extends in an elliptical form and amajor axis of the ellipse is always held in the working progressingdirection indicated by an arrow in the diagram, and the laser beam isradiated onto the point 227 at the highest temperature on theirradiation surface.

Consequently, the working point of the laser beam is most efficientlypreheated, so that the working is performed by use of the minimum laserenergy and the thermal distortion also becomes minimum.

On the other hand, the NC program by which the location of the plasmagun 110 is controlled is obtained by a simple arithmetic operation fromthe main program which determines the contour to be cut out.

As described above, in the laser machining apparatus shown in FIG. 1,the auxiliary energy is always radiated onto the portion which isprecedent in the working progressing direction for the irradiation pointof the main laser beam, so that the heating by the auxiliary energy iseffectively performed, thereby enabling energy efficiency and workingaccuracy of the apparatus to be improved.

FIG. 3 illustrates an embodiment of the laser machining apparatus inwhich a plasma jet as auxiliary energy is irradiated on a workpiece fromthe side opposite the working laser beam in accordance with the presentinvention.

In FIG. 3, reference numeral 301 represents a laser generator; 302 is aprism; 303 a focusing lens; 304 a plasma generating apparatus; 305 apower supply unit; 306 a control unit to control the laser generator 301and power supply unit 305; 307 a workpiece; 308 a cross slide table; 309a traveling table movable in the direction of the X axis of the crossslide table; 310 a traveling table movable in the direction of the Yaxis; 311 a base; 312 and 313 motors; and 314 a numerical control unit.

There are omitted means for supplying the cooling fluid and gas to theplasma generating apparatus, means for supplying a desired gas to theworking portion, means for atmosphere controlling, and further means fordraining vapor and gas which are generated from the working portion.

Similarly to the case of the embodiment shown in FIG. 1, any of the gaslaser, liquid laser, solid state laser, and semiconductor laser can beused for the laser generator 301.

The laser beam generated from the laser generator 301 is reflected bythe prism 302. The laser beam reflected by the prism 302 is focused bythe focusing lens 303 and is converged onto the point to be worked onthe workpiece 307.

In the embodiment, the plasma generating apparatus 304 is attached atthe central portion of the base 311 of the cross slide table 308. Thelaser beam generated from the laser generator 301 is irradiated on theworkpiece 307 from the direction opposite to that of the plasma from theplasma jet generating apparatus 304 such that they sandwich theworkpiece therebetween. Alternatively, the plasma generating apparatus304 may be disposed above the workpiece 307 and the laser generator 301may be disposed at the location of the plasma generating apparatus 304at the lower location in the diagram or may be disposed below the plasmagenerating apparatus 304. Otherwise, the laser beam generated from thelaser generator 301 may be radiated to the workpiece 307 from thelocation of the plasma generating apparatus 304 while the plasma may beirradiated from the upper side so that they sandwich the workpiece 307therebetween by means of suitable combination of prisms, reflectingmirrors or the like.

A voltage is applied to the plasma generating apparatus 304 by the powersupply unit 305, so that the apparatus 304 generates the plasma.

In this embodiment, the plasma generating apparatus 304 for generating aplasma jet, namely, non-moving type plasma is used; however, a plasmagenerating apparatus for generating a plasma arc, i.e., moving typeplasma may be used.

The control unit 306 controls the laser generator 301 and power supplyunit 305, thereby changing power densities of the laser beam generatedfrom the laser generator 301 and of the plasma jet generated from theplasma generating apparatus 304. At the same time, the laser beam andplasma jet can be respectively set to be continuous, or strong and weak,or pulse oscillatory. However, it is desirable to set at least one ofthem to have pulse oscillation.

In the embodiment, for example, the plasma jet is set to be continuousand the laser beam is set to be pulsating. But, when a high degree ofworking accuracy is required, the laser beam can be switched between thecontinuous oscillation and the pulse oscillation, or the intermittentlight emission by a proper means in accordance with the contour whichshould be cut out from the workpiece 307.

In the above case, the laser generator 301 is constituted and controlledin the manner such that it performs continuous oscillation at therectilinear portion of the contour to be cut, while it performs pulseoscillation when a curved portion having a small curvature or a cornerportion is to be worked.

The workpiece 307 is attached to the traveling table 309 which ismovable along the X axis of the cross slide table 308.

The traveling table 309 is formed as a frame by cutting out the centralportion of a plate-like member. The traveling table 310 is movable alongY-axis and has a longitudinal hole extending in the Y-axis direction atits central portion. These traveling tables 309 and 310 are constitutedsuch that when the laser beam and plasma jet are arranged to face eachother so as to sandwich the workpiece 307 therebetween and are radiatedto perform the working, they do not obstruct the radiation of the plasmajet or laser beam.

The motor 312 moves the traveling table 309 in the direction of the Xaxis, while the motor 313 moves the traveling table 310 in the directionof the Y axis in the diagram.

Both motors 312 and 313 are connected to the numerical control unit 314.The numerical control unit 314 controls the motors 312 and 313 inaccordance with a predetermined program, thereby allowing the workpiece307 attached to the traveling table 309 to be moved two-dimensionally inthe same plane so that the workpiece is cut out along a desired contour.

The control unit 306 is connected to the numerical control unit 314.When the numerical control unit 314 controls the motors 312 and 313 andthereby determines the speed and direction for cutting of the workpiece307, a signal to control the control unit 306 is also generated from thenumerical control unit 314. In response to the signal, the control unit306 controls powers of the laser generator 301 and power supply unit305.

Further, in the case where a high degree of working accuracy isrequired, the control unit 306 can set the laser beam generated from thelaser generator 301 to the continuous oscillation or pulse oscillationin accordance with the speed and contour for cutting the workpiece 307.

The laser beam generated by the laser generator 301 is reflected or itsoptical path is changed by the prism 302 and other reflecting mirrorswhich are appropriately provided. The laser beam is focused by thefocusing lens 303 and is converged onto the irradiation point of theworkpiece 307.

On the other hand, the plasma jet generated by the plasma generatingapparatus 304 is radiated from the back side of the workpiece 307 to theposition corresponding to the irradiation point of the laser beam or tothe location which is slightly precedent in its working advancingdirection.

The workpiece 307 attached to the traveling table 309 in the X-axisdirection is moved two-dimensionally in the same plane in response to acommand from the numerical control unit 314 in accordance with apredetermined program, so that it is cut along a desired contour.

When the workpiece 307 is cut by the energies of the laser beam andplasma jet, since the workpiece 307 is heated to a constant temperatureby the plasma jet, the power density of the laser beam can be set lowerthan that in the case of the working only by the laser beam. Therefore,the laser generator 301 with a low power can be used, so that theapparatus becomes less expensive.

In addition, since the laser radiating apparatus and the plasmagenerating apparatus can be separately installed without combining them,there is less restriction on design and the arrangement can besimplified with its easy handling.

On the other hand, in the embodiment shown in FIG. 3, the laser beam andplasma have been disposed on the same axis. However, they may bearranged so that their axes cross at an angle of a few degrees to tensof degrees. Furthermore, instead of fixing the relative locations of thelaser beam and plasma, it is also possible, for instance, to control thelocation and position of the plasma generating apparatus so that theradiating position of the plasma can be always precedent from theradiating position of the laser beam in the working progressingdirection.

FIG. 4 illustrates another embodiment of the laser machining apparatusin which a laser beam as auxiliary energy is radiated on a workpiecefrom the side opposite the working laser beam.

In FIG. 4, numeral 401 indicates a laser radiating apparatus to radiatea laser beam from the upper side of a workpiece; 401' is a laserradiating apparatus to radiate a laser beam from the lower side of theworkpiece; 402 and 402' housings; 402a and 402a'output ports at the endsof the above housings; 403 and 403' laser generators; 404 and 404'focusing lenses; 405 and 405' working gas supply tubes; 406 and 406'working gas supplying apparatuses each for supplying a working gas suchas a halogen gas or the like; 407 a workpiece; 408 and 409 cross slidetables to move the workpiece 407 in the directions of the X and Y axesrespectively ; 410 a base on which the cross slide tables are mounted;411 and 412 motors to drive the cross slide tables; 413 a control unitto control the laser generators 403 and 403' and the working gassupplying apparatuses 406 and 406'; and 414 a numerical control unit tototally control the motors 411 and 412 to drive the cross slide tablesand the control unit 413 in accordance with a predetermined program.

When working, the laser beams generated from the laser generators 403and 403' are focused by the focusing lenses 404 and 404' and areradiated to the working portion of the workpiece 407 from the upper andlower sides thereof through the output ports 402a and 402a' of thehousing 402 and 402'. At the same time, the working gas such as halogenor the like supplied from the working gas supplying apparatuses 406 and406' are discharged onto both upper and lower sides of the workpiece.The laser beam from the lower laser generator 403' is radiated to theportion corresponding to the irradiation point of the laser beam fromthe upper laser generator 403 or to the portion which is slightlyprecedent therefrom in its working progressing direction, so that theworking is carried out.

The working gas is not limited to halogen, and furon gas of variouskinds, water vapor, pure oxygen gas or proper mixture of these gases maybe used in accordance with the material and cutting shape or the like ofthe workpieces.

In the laser machining apparatus in the embodiment of FIG. 4, theworkpiece 407 is worked by the laser beams and working gases from bothof the upper and lower surfaces simultaneously; thus, even in the casewhere a thick workpiece is cut and worked, the working can be performedin a short time and with high accuracy.

Namely, in case of working by radiating the laser beam only from oneside of the workpiece, the cutting and working could be performed at aworking speed of 1.5 m/min according to the following experiment. Thatis, a C0₂ laser having a wavelength of 10.6 μm and a power of 350 W wasradiated to the S55C steel having a thickness of 2.5 mm from only oneside while discharging pure oxygen gas coaxially with the laserradiation beam. In addition, a workpiece of the same material with athickness of 8 mm was worked under the same conditions. Thus, thecutting was done at a working speed of 1 m/min. In these case, theworking accuracy was ±0.08 mm. On the other hand, the experiment wascarried out using the laser machining apparatus according to the presentinvention as shown in FIG. 4. Namely the C0₂ laser having a wavelengthof 10.6 μm and a power of 250 W was used for the upper laser generator403. As the lower laser generator 403', a generator similar to the upperone is used, while a power of such a generator 403' was set at 80 W. TheS55C material having the same thickness of 2.5 mm as that which had beenused in the foregoing experiment was worked while discharging pureoxygen from the sides of the respective laser radiation beams. Thus, theworking could be effected at a working speed of 2.5 m/min. In addition,a workpiece of the same material with a thickness of 8 mm was workedunder the same conditions, so that the working could be performed at aworking speed of 3.5 m/min and the working accuracy of ±0.05 mm. Theworking speed was clearly increased by about three times as comparedwith the conventional system and the working accuracy was remarkablyimproved.

Further, although it was difficult to work 18-8 stainless steel of athickness of 2.5 mm by the conventional laser machining apparatus, it ispossible to easily work it by the laser machining apparatus according tothe present invention. Also, such a stainless steel having a thicknessof up to 8 mm could be worked by the present apparatus.

FIG. 5 illustrates an embodiment of the laser machining apparatus inwhich a glow or corona discharge as auxiliary energy is radiated aroundthe working laser beam irradiated portion.

In FIG. 5, numeral 501 denotes a pressure reducing chamber; 502 is apacking; 503 a cover member to sealingly close the pressure reducingchamber 501; 504 and 505 housings for the laser radiating apparatus;504a an opening formed at the end of the housing 504; 504b a flangeformed integrally with the housing 504; 506 a laser generator attachedto the housing 505; 507 a focusing lens attached in the housing 505; 508a fixing member to fix the focusing lens; 509 a motor; 509a a shaft ofthe motor; 510 an exhausting pipe; 511 and 512 valves; 513 and 514vacuum vessels having appropriate volumes; 515 a diffusion pump; 516 amechanical booster; 517 a rotary vacuum pump; 518 a halogen gassupplying apparatus to supply a halogen gas or a gas of halogencompound; 519 a pressure control valve; 520 an electrode attached to thehousing 504; 521 a workpiece; 522 and 523 cross slide tables which aredisposed in the pressure reducing chamber 501 and move the workpiece521; 524 a turntable mounted on the cross slide tables for applying therotational motion to the workpiece 521; 525, 526 and 527 motors torespectively drive the cross slide tables and turntable; and 528 a powersupply unit which is connected between the electrode 520 and theworkpiece 521 or the turntable 524 on which the workpiece is placed.This power supply unit 528 supplies a direct current at a high voltage,a high frequency, or a pulsating current to heat the workpiece 521 dueto glow or corona discharge. The electrode 520 may be disposed at aproper location such as at the inner surface of the cover member 503.

The cross slide tables 522 and 523 and turntable 524 are fixed in thepressure reducing chamber 501. The workpiece 521 is fixed on theturntable 524. The pressure reducing chamber 501 is sealingly closed bythe cover member 503 through the packing 502. The inside of the pressurereducing chamber 501 is maintained at a degree of vacuum, e.g., 1-10Torr or less, which is necessary for the operation of the diffusion pump515. Such a degree of vacuum can be relatively easily derived by themechanical booster 516 and rotary vacuum pump 517. Also, the inside ofthe vacuum vessel 514 is reduced to a pressure of 10⁻² -10⁻³ Torr. Ahalogen or halogen oxide gas is supplied from the gas supplyingapparatus 518 through the pressure control valve 519 into the pressurereducing chamber 501 which was made vacuous. Preferably, the halogen gasat a low pressure is jetted by being directed near the working portionof the workpiece 521 by a nozzle whose position can be adjusted andcontrolled.

The laser generator 506 is attached to one end of the housing 505. Inthis embodiment, although the system having a single laser radiatingapparatus has been illustrated, the number of the laser generators maybe changed arbitrarily in accordance with the working conditions such asthe material, shape, size, etc., of the workpiece 521.

The laser beam generated from the laser generator 506 is converged bythe focusing lens 507 and is radiated onto the working portion of theworkpiece 521.

At the joint portion of the housings 504 and 505, the outer diameter ofthe housing 505 is set to be substantially equal to the inner diameterof the housing 504 and the housing 505 is slidably attached to thehousing 504. The motor 509 is attached to the outer surface of thehousing 505. Its shaft 509a is threaded and engages the female threadsformed on the flange 504b of the housing 504. Therefore, the housing 505can be moved in the direction of the X axis in response to the rotationof the motor 509 attached thereon. The electrode 520 is attached to theopening end of the housing 504 to face the workpiece 521. A directcurrent, a high frequency current or a pulsating current at a highvoltage is supplied from the power supply unit 528 between the electrode520 and workpiece 521, thereby heating the workpiece 521 due to the glowor corona discharge. Preferably, the working portion is moreconcentratedly heated by a close arrangement of the electrode 520 andthe workpiece 521 as shown in FIG. 5.

In addition, in accordance with a predetermined program, a numericalcontrol unit (not shown) controls: the motor 509 to move the housing 505along the X axis; the motors 525 and 526 to move the cross slide tables522 and 523 respectively; the motor 527 to rotate the turntable 524; theadjustment of a degree of vacuum in the pressure reducing chamber 501;the quantity of halogen gas which is supplied from the halogen gassupplying apparatus 518; the power supply unit 528 which supplies apredetermined voltage between the electrode 520 and the workpiece 521thereby causing the glow or corona discharge or the like in the pressurereducing chamber 501 using the workpiece 521 as a pole; etc.

In the case where the working is carried out by the laser machiningapparatus according to the present invention as shown in FIG. 5, theinside of the pressure reducing chamber 501 is kept at about 1-10 Torror less by the mechanical booster 516 and rotary vacuum pump 517. When ahigh voltage is applied from the power supply unit 528 between theelectrode 520 (anode) and the workpiece 521 (cathode) in such a loweredpressure state, a glow discharge is generated. Thus, the above dischargevoltage is reduced and the glow discharge is maintained constantly,whereby the workpiece 521 is appropriately heated. The halogen gas suchas C1₂, F₂ or the like or the gas of halogen compound such as Freon orthe like is supplied thereto from the gas supplying apparatus 518.Thereafter, the laser beam from the laser generator 506 is focused toabout 10⁴ -10⁸ W/cm² by the focusing lens 507 and is radiated to theworking portion of the workpiece 521. Consequently, the temperature ofthe working portion on the surface of the workpiece 521 is raised and apart of metal molecules of the working portion are ionized and removed,thereby performing the working.

Therefore, the workpiece 521 is worked effectively in a short time underthe action of the glow discharge and the action of the heat produced asthe result of the halogen gas or the halogen compound gas emitted to thelaser beam.

In this case, the auxiliary energy is not limited to the glow or coronadischarge but an arc discharge may be used.

As described above, in the case of this embodiment, the corona or glowdischarge as auxiliary energy is generated at the location slightlyshifted from the irradiation point of the main working laser beam suchthat it surrounds the irradiation point of this laser beam. Therefore,the auxiliary energy is applied efficiently and an arrangement of thesystem is simplified.

Another embodiment of the laser machining apparatus of the presentinvention will now be described with reference to FIG. 6 in whichabrasive grain is discharged to the working portion in addition to thecorona or glow discharge or arc discharge as the auxiliary energy,thereby performing the working.

In FIG. 6, the same parts and components as those shown in FIG. 5 aredesignated by the same reference numerals. Further, numeral 529 denotesan abrasive grain discharging apparatus attached to the outer surface ofthe housing 504; 530 is a rotary disk; 531 a rotary disk attaching base;532 a crown gear; 533 a motor; 534 a pinion gear which is attached to ashaft of the above motor and is in engagement with the above crown gear;535 an abrasive grain; 536 an abrasive grain tank to supply the abrasivegrain 535 to the abrasive grain discharging apparatus 529; 537 acompressor which compresses the halogen gas or gas of halogen compoundin the pressure reducing chamber 501 and supplies it to the abrasivegrain discharging apparatus 529; and 538 a box to collect the abrasivegrain.

In the system of this embodiment, in addition to the system shown inFIG. 5, the abrasive grain 535 is discharged and supplied at a highpressure to the working portion of the workpiece 521.

Namely, the rotary disk 530 is formed annularly so as to surround theouter surface of the housing 504 and the abrasive grain dischargingapparatus 529 is attached to one end thereof. This rotary disk 530 isrotatably attached to the base member 531 fixed to the housing 504. Thecrown gear 532 is fixed to the rotary disk 530 coaxially with its rotaryaxis so as to come into engagement with the pinion gear 534 attached tothe shaft of the motor 533 and is rotated in association with therotation of the motor 533.

The quantity of abrasive grain which should be discharged from thedischarging apparatus 529 and the rotation of the motor 533 for thedischarging apparatus 529 are together controlled by a numerical controlunit (not shown) similarly to the system shown in FIG. 5.

In execution of the working by this laser machining apparatus, theinside of the pressure reducing chamber 501 is maintained at about 1-10Torr or less by the mechanical booster 516 and rotary vacuum pump 517and the like. In this condition, when a voltage is applied from thepower supply unit 528 between the electrode 520 (anode) and theworkpiece 521 (cathode), the glow discharge is produced. Then, theabove-mentioned discharge voltage is reduced and the glow discharge iskept constantly, thereby the workpiece 521 is heated. The halogen gassuch as C1₂, F₂ or the like, or the halogen compound gas such as Freonis supplied from the gas supplying apparatus 518 thereto. Thereafter,the laser beam from the laser generator 506 is focused at about 10⁴ -10⁸W/cm² by the focusing lens 507 and is radiated to the working portion ofthe workpiece 521. Further, in addition to the above operation, theabrasive grain 535 is discharged at a high pressure from the abrasivegrain discharging apparatus 529 toward the portion to be worked of theworkpiece 521. The supply of the abrasive grain 535 by the dischargingapparatus 529 is carried out so as to be precedent in the workingprogressing direction at the irradiation point of the laser beam.

The current of the glow discharge concentratedly flows through theportion to be worked of the workpiece 521. At the same time, atemperature of the portion is raised by the laser beam from the lasergenerator 506. Thus, a part of metal molecules of the surface of theworkpiece 521 are ionized and removed. Furthermore, since the abrasivegrain 535 is supplied at a high pressure to the working portion from theabrasive grain discharging apparatus 529, the workpiece 521 is worked ina short time by the combination of these various actions.

That is, the workpiece 521 is worked effectively in a short time underthe action of the glow discharge, the thermal and chemical actions whichare caused as the result of the halogen gas or gas of halogen compoundbeing radiated by the laser beam, and the action of the abrasive grain535 supplied at a high pressure from the abrasive grain dischargingapparatus 529.

As described above, in the system shown in FIG. 6, it is possible toperform the working by desired combination of the glow discharge, laserbeam, halogen gas or halogen compound gas, and abrasive grain.Therefore, even if the working is particularly difficult, such as incase of a metal or the like, the working can be certainly carried out ina short time.

Referring now to FIG. 7, there is illustrated an embodiment of the lasermachining apparatus in which a Xenon light is radiated to the locationwhich is slightly shifted from the irradiation point of the main workinglaser beam and further a plasma gas and a high-pressure fluid aresupplied, thereby working is carried out.

In FIG. 7, numeral 701 represents a housing; 701a is an opening end atthe point of the housing 701; 702 a laser generator; 703 a Xenon lightsource; 704 a high-pressure fluid supplying apparatus; 705 a plasma gassupply tube; 706 a reflecting mirror; 707 a focusing lens; 708 a focalpoint adjusting pipe to which the above focusing lens is attached andwhich is slidably attached to the housing 701; 709 a motor to move thefocal point adjusting pipe 708; 710 a funnel-like bulkhead nozzle toseparate the opening portion 701 of the housing into the exhaust nozzlefor the laser beam and high-pressure fluid jet and into the exhaustnozzle for the plasma gas; 711 a rotary disk to which the Xenon lightradiating apparatus 703 is attached; 712 a rotary disk attaching base;713 a crown gear; 714 a pinion gear which is attached to the rotary axisof the motor 715 and comes into engagement with the crown gear; 716 aworkpiece; 717 and 718 cross slide tables to move the workpiece 716along the X and Y axes respectively; 719 a turntable mounted on thecross slide table 717 for exerting the rotational motion to theworkpiece 716; and 720, 721 and 722 motors to drive the cross slidetables and turntable respectively.

As the laser generator 702, a gas laser such as a C0₂ laser, He-Ne laseror the like, a solid state laser such as a ruby laser, YAG laser or thelike, etc. are used. In addition, a power of such a laser beam can beincreased by using a Q-switching method or the like as necessary.

The laser beam generated from the laser generator 702 is focused by thelens 707 and is reflected by the reflecting mirror 706 and passesthrough the bulkhead nozzle 710 and is radiated on the workpiece 716.The position of a focal point is adjusted by moving the focal pointadjusting pipe 708 by driving the motor 709. A small hole 706a is formedat the central portion of the reflecting mirror 706. The high-pressurefluid jet such as acid, alkali or the like which is jetted as a thinline form from the high-pressure fluid supplying apparatus passesthrough the small hole 706a and is jetted onto the workpiece 716together with the laser beam.

Similarly to the plasma gun 110 in the foregoing embodiment shown inFIG. 1, the Xenon light source 703 is rotated around the optical axis ofthe laser beam reflected by the reflecting mirror 706 by the rotarymechanism consisting of the rotary disk 711, crown gear 713, pinion gear714, and motor 715. The Xenon light emitted from the apparatus 703 isradiated to the location which is always precedent from the workinglaser beam in the direction of the working progressing direction on thesurface of the workpiece.

The plasma gas imported from the gas supply tube 705 is dischargedtoward the working portion through the opening portion 701a at an end ofthe housing. In this case, the gas for the laser working may be alsosupplied together with the plasma gas from the plasma gas supply tube705. The laser working gas may be led into the housing 701 at the upperportion than the bulkhead nozzle 710 and may be discharged through thebulkhead nozzle 710.

In addition, in accordance with a predetermined program, a numericalcontrol unit (not shown) totally controls: the motor 709 to move thefocal point adjusting pips 708; the motor 715 to rotate the Xenon lightsource 703; the motors 720, 721 and 722 to drive the cross slide tablesand turntable respectively; quantities of plasma gas and high-pressurefluid to be supplied; etc.

In case of working by the laser machining apparatus shown in thisembodiment, the laser beam focused is radiated to the working portionand at the same time the water or fluid of acid, alkali or the likeselected in dependence upon the material and the like of the workpieceis discharged as a jet from the high-pressure fluid supplying apparatus704 at a high pressure toward the working portion. Also, the plasma gasis simultaneously supplied to the periphery thereof. Further, the Xenonlight from the apparatus 703 is radiated to the portion which isslightly precedent from the radiating position of the laser beam.

Therefore, the plasma gas supplied to the working portion is mostefficiently preheated by the focused laser beam. Further, under theaction of a pressure of water discharged at a high pressure from thehigh-pressure fluid supplying apparatus 704, the working to the portionto be worked is carried out. Additionaly, the molecules of watersupplied to the working portion are ionized by the laser beam. Sincethis ionized situation is very unstable, the ionized water molecules arerecombined tending to instantly return to their original state. Upon therecombination of the ionized water, a high energy is emitted.

Consequently, the workpiece 716 is extremely efficiently worked underthe actions of the pressure of water which is discharged at a highpressure together with plasma gas and of the heat generated when thewater molecules are ionized and recombined, as well as the actions oflaser beam and Xenon light.

Namely, for example, in the case where a C0₂ laser of 200 W is used andthe working is performed while supplying water at a rate of 0.05 cc/min,a roughness of the worked surface of 10 μRmax and a working speed of0.23 g/min could be obtained. On the other hand, in case of performingthe working using a conventional general laser machining apparatus, theroughness was 12 μRmax and the working speed was 0.06 g/min.

Water is ordinarily used as a fluid which is supplied from thehigh-pressure fluid supplying apparatus 704, but an acid fluid is usedin the case where material of the workpiece 716 is ceramics, alumina,glass, or the like. Further, in the case of working metal, metal havingan oxidized surface, titanium dioxide, or material partially oxidized,etc., it is desirable to use an alkali fluid.

When the path of the high-pressure fluid jet which is discharged fromthe fluid supplying apparatus 704 coincides with the optical axis of thelaser beam and the path is long, the fluid is heated by the laser beam,so that more than a part thereof is evaporated or the jet causes thelaser beam to be diffused. In such a case, it is preferable to adopt aconstitution such that the Xenon light radiating apparatus 703 andhigh-pressure fluid supplying apparatus 704 are attached so that theirlocations are exchanged in FIG. 7. In this case, a radiating diaphragmdiameter of Xenon light having the same axis as the laser beam may beset to be larger than that of laser beam, while the beating point of thehigh-pressure fluid jet against the workpiece may be adjusted and setinto the radiating location of the laser beam or into the portionalready worked where it is slightly delayed in the working progressingdirection.

Next, with reference to FIG. 8, an embodiment will be explained wherebya gas discharged from the working laser generator is used as a part ofplasma gas for generation of a plasma jet as an auxiliary energy.

In case of using a gas laser for the laser generator, C0₂ laser, He-Nelaser, Ar laser, etc. are known as a gas laser. For example, in case ofthe C0₂ laser, a mixed gas containing C0₂, Ne, He, N₂, etc. is sealinglyenclosed in the laser tube and is allowed to flow therethrough and a gasdischarge is generated, thereby causing a laser beam to be oscillated.

At this time, if the temperature of the laser gas exceeds apredetermined value (e.g., 200° C.), the laser beam will not efficientlyoscillate. Therefore, the laser gas is allowed to flow through the lasertube at a high speed and it is cooled by being circulated by a gassupplying apparatus, and at the same time a part thereof is dischargedand a new gas is supplied continuously.

On the other hand, the plasma generating apparatus generates an arcdischarge by application of a voltage between the electrodes from apower supply unit and supplies the plasma gas to the portion around thearc discharge, thereby generating a plasma. In ordinary plasma working,the rate of the cost of gas to the running cost reaches more than 80%.

In a conventional well-known system which works using both a lasergenerator and a plasma generating apparatus, the laser gas and plasmagas are supplied from individual sources and the discharged gas from thelaser generator is drained to the outside. In addition, a large amountof plasma gas is consumed and it is also necessary to supply a workinggas, shielding gas, etc. Thus, the cost of gas occupies almost of therunning cost and therefore it is very uneconomical.

Therefore, in one embodiment of the laser machining apparatus accordingto the present invention shown in FIG. 8, the discharged gas from thelaser generator is used as a part of plasma gas of the plasma generatingapparatus, thereby eliminating the waste gas and omitting or simplifyingthe cooling apparatus for the laser gas.

In FIG. 8, numeral 801 denotes a laser generator; 802 is a laser tube;803 discharge electrodes; 804 and 804', reflecting mirrors arranged onboth ends of the laser generator 801; 805 a laser gas supplyingapparatus; 806 and 806' laser gas supply tubes; 807 a gas transmittingtube for introducing the discharged gas from the laser generator 801 toa plasma generating apparatus; 808 a plasma gas supplying apparatus; 809a housing; 810 a laser beam reflecting mirror; 811 a focusing lens; 812a workpiece; 813 the plasma generating apparatus; 814 one electrode forgenerating a plasma; 815 a plasma torch nozzle; 815a an opening at theend of the nozzle 815; 816 a power supply unit for generating a plasma;and 817 a resistor inserted. A cooling water jacket provided around theperipheral of the laser tube 802, or a cross slide table and a turntableand the like to move the workpiece 812 are omitted in the diagram.

The discharge electrodes 803 cause the laser gas in the laser tube 802to generate the discharge and excite the laser gas molecules, therebygenerating a laser beam.

The reflecting mirror 804 totally reflects the laser beam generated inthe laser tube 802, while the reflecting mirror 804' is semitransparentand transmits a part of the laser beam.

Thus, the laser beam generated due to discharge in the laser tube 802successively causes the induced radiation and resonates between thereflecting mirrors 804 and 804' to increase its strength, so that itpasses through the reflecting mirror 804' and is sent as a beam.

The laser gas supplying apparatus 805 sends a laser gas into the lasertube 802 through the laser gas supply tube 806; allows the gas to flowin the laser tube 802 at a high speed; then collects it from the otherlaser gas supply tube 806'; and cools it; then circulates itcontinuously.

At this time, the laser gas supplying apparatus 805 sends about, e.g.,two-fifths of the collected laser gas to the gas supply tube 807 asexhausted gas and circulates the remaining gas of about three-fifths. Onthe other hand, the lack of gas due to the exhausting is newlysupplemented by the laser gas supplying apparatus 805.

Since the composition of the laser gas is different from that of theplasma gas and a quantity of discharged gas from the laser generator 801is less than the quantity of plasma gas to be used in the plasmagenerating apparatus (according to experiments, the discharged gas froma laser generator of 1.2 kW is about 100 l/h, while the plasma gasnecessary for a plasma generating apparatus of 1.5 kW is about 800 l/h),in order to use the discharged gas from the laser generator as theplasma gas, the composition of gas has to be changed and at the sametime the lack of gas has to be supplemented.

For reference, an example of the composition of a laser gas and a plasmagas as a volume ratio is as follows;

Laser gas

    Ar:He:C0.sub.2 :N.sub.2 ≈0-0.5:9:1:3

Plasma gas

    Ar:He:C0.sub.2 :N.sub.2 ≈0.5-1:3:1:3

Therefore, the plasma gas supplying apparatus 808 supplements the lackof gas at a proper rate for the discharged gas from the laser generator801 and adjusts it so that suitable composition and quantity for aplasma gas can be obtained, and thereafter supplies it into the plasmagenerating apparatus 813.

The reflecting mirror 810 is attached to the housing 809 and reflectsthe laser beam generated from the laser generator 801, thereby changingits optical path.

The focusing lens 811 focuses the laser beam reflected by the reflectingmirror 810 and collects it onto a working point on the workpiece 812.

The power supply unit 816 applies a sufficient voltage of the order atwhich the discharge can be developed among the electrode 814 (cathode)of the plasma generating apparatus 813 and the plasma torch nozzle 815(anode) and the workpiece 812 (anode). In this case, an appropriatepotential difference is given by the resistor 817 between the nozzle 815(anode) and the worlPiece 812 (anode).

The plasma generating apparatus 813 is arranged on the same axis as theoptical axis of the laser beam and generates a plasma jet by beingsupplied with plasma gas from the gas supply tube 807 and a voltage fromthe power supply unit 816. This plasma is radiated so as to surround theperipheral of the irradiation point of the laser beam.

The laser beam focused by the lens 811 is, therefore, radiated onto theworking point of the workpiece 812 and an impact of a high-energydensity is applied, so that the portion around the working point isheated by the plasma, thereby allowing the working such as welding,cutting, fusion, etc. to be executed very efficiently.

The workpiece 812 is put on an attaching base of the cross slide table(not shown) connected to a numerical control unit (not shown) and istwo-dimensionally moved in response to a command from the numericalcontrol unit. Therefore, a desired contour is cut out of the workpiece812.

In the laser machining apparatus as shown in FIG. 8, when a lasergenerator of 1 kW and a plasma generating apparatus of 400 W were used,by adding a gas of about 200 l/h to the discharged gas from the lasergenerator, it could be used as the plasma gas.

In addition, even if the laser gas is not cooled in particular, thelaser oscillation will not be disturbed, so that the cost of the systemand its running cost could be reduced.

A quantity of discharged gas from the laser generator 801 increases asthe scale of laser generator becomes large. Therefore, the arrangementshown in FIG. 8 is very advantageous for a laser machining apparatuswhich uses both a large-sized laser generator and a plasma generatingapparatus.

Next, another embodiment of the laser machining apparatus according tothe present invention will be explained with reference to FIG. 9.

The embodiment shown in FIG. 9 is also constituted in the manner suchthat a plasma jet as auxiliary energy is radiated to a locationdifferent from the irradiation point of the laser beam, namely, onto theopposite surface of the workpiece in accordance with the fundamentalprinciple of the present invention. Further, in the embodiment, theworking fluid is supplied to the working portion and the working is donewhile more than 80% of the working fluid is being evaporated.

In a conventional laser machining apparatus, in the case of workingquartz glass or the like which is relatively difficult to be worked, thequartz glass is kept in the working fluid and the working is done whileradiating the laser beam through the working fluid to the quartz glass.However, unless the laser beam has a proper wavelength, almost all ofthe laser beam will be absorbed in the working fluid. Even if awavelength of laser beam is suitable, there is a problem that it takes along time to work.

In the embodiment shown in FIG. 9, a working fluid such as an acid oralkali fluid or the like is supplied onto the surface of the workpieceand over 80% of the working fluid supplied is evaporated by the laserbeam, effecting the working.

In FIG. 9, numerals 901 and 902 denote housings; 902a is an opening atthe end of the housing 902; 903 a laser generator; 904 a reflectingmirror; 905 a focusing lens; 906 a motor to move the housing 902 alongthe housing 901 in the direction of Z axis, thereby to adjust a focalpoint of the laser beam; 907 a working fluid supplying apparatus; 908 arotary disk; 909 a rotary disk attaching base; 910 a crown gear; 911 amotor; 912 a pinion gear which is attached to the shaft of the motor 911and is in engagement with the crown gear 910; 913 a tube for supplying alaser working gas such as halogen or the like; 914 a gas supplyingapparatus; 915 a workpiece; and 916 a plasma generating apparatus forradiating a plasma to the workpiece 913 from the side opposite to theworking laser beam.

A cross slide table and a turntable to move the workpiece 915 areomitted.

The laser beam generated from the laser generator 903 is reflected bythe reflecting mirror 904 and its optical path is changed, thereafter itis focused by the lens 905 and is radiated onto the working point on theworkpiece 915. At this time, a halogen gas, furon gases of variouskinds, oxygen, or mixtures of these gases which were supplied from theworking gas supplying apparatus 914 are simultaneously discharged fromthe opening 902a of the housing 902 toward the working portion ontowhich the laser beam has been radiated. Further, a plasma jet isradiated from the plasma generating apparatus 916 onto the oppositesurface of the workpiece 915, so that the workpiece is sufficientlyheated and is efficiently worked.

A working fluid which is selected in accordance with the material of theworkpiece 915 and working conditions, for instance, an acid or alkaliworking fluid such as HCI, dilute H₂ SO₄, KOH aqueous solution, HFaqueous solution, hydrocarbon, etc. is supplied from the working fluidsupplying apparatus 907 to the radiating portion of the laser beam. Thisworking fluid is supplied by a predetermined limited quantity as a thinjet fluid stream or mist droplets, or further as a spray mist with a gassuch as an inert gas or the like. The working fluid supplying apparatus907 is rotated by the rotating mechanism consisting of the rotary disk908, crown gear 910, pinion gear 912, and motor 911 around the opticalaxis of the laser beam reflected by the reflecting mirror 904 is rotatedin similar manner as the plasma gun 110 in the embodiment shown inFIG. 1. The working fluid discharged from the apparatus 907 is suppliedto the location which preferably precedes the working laser beam on thesurface of the workpiece in the working progressing direction.

In accordance with a predetermined program, a numerical control unit(not shown) totally controls: the motor 906 to move the housing 902 inthe direction of the Z axis in the diagram; the motor 911 to rotate therotary disk 908; motors (not shown) to drive the cross slide table andturntable for moving the workpiece 915; the supply location and supplyquantity of the working fluid from the working fluid supplying apparatus907; a supply quantity of the gas by the working gas supplying apparatus914; and the like.

In the case of working by the laser machining apparatus of the presentinvention with such an arrangement as mentioned above, the working fluidsupplied to the working portion of the workpiece 915 is heated by theworking laser beam and plasma heat from the plasma generating apparatus916 and the working is done while more than about 80% of the workingfluid is evaporated. Therefore, the working is extremely efficientlyperformed without the laser beam being absorbed by the working fluid.Further, since a halogen gas, furon gases of various kinds, oxygen etc.,or mixtures of them, which may be selectively chosen in accordance withthe material of the workpiece, are supplied as the working gas throughthe opening 902a of the housing 902, material such as quartz glass orthe like which is difficult to be worked by an ordinary laser workingcan be also easily worked.

Namely, for example, quartz glass having an outer diameter of 38 mm andan inner diameter of 4 mm was worked at a working feeding speed of 35mm/min by use of a CO₂ laser of 100 W while supplying an aqueoussolution of HF as a working fluid at a rate of 0.02 cc/min. As a result,the above quartz glass could be cut at a rate of 162 mm/min. On thecontrary, when a similar quartz glass was worked using a conventionallaser machining apparatus, it took several times longer than that by thesystsm of the present invention.

As described above, according to the laser machining apparatus of theembodiment shown in FIG. 9, even quartz glass or the like which isdifficult to be worked in particular can be worked within a short timeirrespective of the material of a workpiece, etc.

Next, an embodiment will be explained with reference to FIG. 10 wherebya plasma is used as auxiliary energy and the plasma is radiated to thelocation which is preceding the working laser beam for the workpiece inaccordance with the fundamental principle of the present invention, anda working fluid to which an ultrasonic energy was applied is supplied tothe working portion or to the portion immediately after working.

In case of laser machining, in the order to remove working debris fromthe working portion or to prevent deterioration of working accuracybecause of change in quality of workpiece due to the heat of the laser,a working fluid is ordinarily supplied to the working portion. However,quick removal of working debris and sufficient cooling effect of theworking portion are not always obtained by merely supplying the workingfluid by ordinary means. To solve this problem, in the embodiment shownin FIG. 10, a working fluid to which ultrasonic energy was applied issupplied to the working portion or a portion immediately after working,thereby effectively removing the working debris and improving thecooling effect and thereby enabling the working to be smoothly performedwith a high degree of accuracy.

In FIG. 10, numeral 1001 denotes a housing; 1002 is a verticallyslidable housing attached to the lousing 1001; 1003 is a motor to adjusta focal point by vertically moving the housing 1002 with respect to thehousing 1001; 1004 a laser generator; 1005 a reflecting mirror; 1006 afocusing lens; 1007 a working gas supplying apparatus; 1008 a plasmagenerating apparatus; 1009 a working fluid supplying nozzle; 1009a anultrasonic vibrator attached to the working fluid supplying nozzle; 1010a rotary disk to which the plasma generating apparatus 1008 and workingfluid supplying nozzle 1009 are respectively attached to the oppositesides on a diameter thereof; 1011 a crown gear fixed to the rotary disk1010; 1012 a motor to rotate the crown gear 1011; 1013 a working fluidsupply tank; 1014 a workpiece; 1015 a cross slide table to move theworkpiece; 1016 and 1017 motors to drive the cross slide table; and 1018a numerical control unit.

The laser beam generated by the laser generator 1004 is reflected by thereflecting mirror 1005 and is focused by the lens 1006 and is radiatedonto the workpiece 1014. At this time, a working gas from the workinggas supplying apparatus 1007 is discharged toward the working portion.

Also, the plasma generating apparatus 1008 is rotated by the rotatingmechanism consisting of the rotary disk 1010, crown gear 1011, motor1012, etc. around the optical axis of the laser beam reflected by thereflecting mirror 1005 in the similar manner as the plasma gun 110 inthe embodiment shown in FIG. 1 is rotated. A plasma generated by theapparatus 1008 is radiated to the location which precedes the workinglaser beam on the surface of the workpiece in the working progressingdirection.

On the other hand, the working fluid introduced from the working fluidsupply tank 1013 to the working fluid supplying nozzle 1009 is jetted tothe surface of the workpiece. In this case, since the working fluidsupplying nozzle 1009 is attached to the side opposite to the plasmagenerating apparatus 1008 on the diameter of the rotary disk 1010, whenthe rotary disk 1010 is rotated such that the plasma is radiated to thelocation which precedes the laser radiating portion, the working fluidfrom the supplying nozzle 1009 is discharged toward the portionimmediately after working by the laser beam.

The working fluid of a predetermined flow rate is fed into the workingfluid supplying nozzle 1009 from the working fluid supply tank 1013 andis discharged through the opening end of the nozzle after addition of anultrasonic vibrational energy by the vibrator 1009a. The ultrasonicvibrator 1009a performs the ultrasonic vibration due to a current from ahigh-frequency power source (not shown). When a vibration of relativelyhigh frequency is required, an electrostrictive vibrator is preferablyused for the vibrator 1009a, while a magnetostrictive vibrator may beused when a relatively low frequency is to be generated. Only onevibrator 1009a may be provided as shown in the embodiment, but it isalso possible to provide a plurality of such vibrators and to apply aplurality of ultrasonic vibrational energies having differentfrequencies to the working fluid.

In accordance with a predetermined program, the numerical control unit1018 controls: the motor 1003 to adjust the focal point of the laserbeam by moving the housing 1002 in the direction of the Z axis in thediagram; the motor 1012 to rotate the plasma generating apparatus 1008and working fluid supplying nozzle 1009 around the optical axis of thelaser beam; the motors 1016 and 1017 to drive the cross slide table1015, etc.

In the case of working by the laser machining apparatus of the presentinvention with such an arrangement as mentioned above, the laser beamgenerated by the laser generator 1004 is radiated onto the workingportion of the workpiece 1014, and a working gas is discharged thereto,and at the same time a plasma jet from the plasma generating apparatus1008 is radiated to the location which precedes the radiating portion ofthe laser beam. At this time, a surplus of the working fluid near theworking poirt is removed due to the evaporation of the working fluid bydischarging the working gas and by radiating the laser beam and plasma,so that the working portion is covered by a layer of the working fluidof a proper amount and the laser beam is radiated through the layer.Thus, the working is very efficiently performed. At the same time, theportion immediately after working is cooled by the working fluid towhich ultrasonic vibrational energy was applied and deformation due tothe heat is prevented, so that only a desired portion is accuratelyworked. In addition, the working debris is effectively removed and theenergy of the laser beam is supplied only to the working point, therebyallowing a working efficiency to be improved.

Particularly, the working fluid to which an ultrasonic vibrationalenergy is applied has a high cooling effect and can present a coolingeffect which is two or more times that in the case of an ordinaryworking fluid. Also, when two or more kinds of ultrasonic vibrationalenergies having different frequencies were applied to the working fluid,it is possible to obtain a cooling effect which is three or more timesthat in the case of an ordinary working fluid.

Furthermore, the working fluid to which an ultrasonic vibrational energywas applied is extremely effective to remove the working chips because aphysical peeling force due to cavitation is applied in addition to theboiling phenomenon caused by the laser beam. Particularly, in the caseof three-dimensional working, it is effective to remove the workingchips from blind holes or narrow gap portions. In addition, the workingchips can be removed within a short time as compared with the case wherean ordinary working fluid is supplied.

In the case where a surface-active agent or the like is mixed with theworking fluid and it is discharged from the working fluid supplyingnozzle 1009 in the form of a foam, the working chips can be furthereffectively removed with the aid of cleaning action due to theemulsifying action as well. In this case, the working fluid which oncebecame foam is broken due to radiation of the laser beam at the workingportion, so that no additional working fluid remains in the workingportion, but the working portion is covered by the working fluid layerof a proper amount, and thus the portion immediately after working iscooled by the working fluid with the ultrasonic vibrational energy.

In experiments using an laser machining apparatus according to thepresent invention as shown in FIG. 10, when a laser generator having apower of 100 W was used and an ultrasonic vibrational energy of 500 kHzand 20 W was applied to the working fluid, the working could be donewith a working surface roughness of 5 μRmax and at a working speed of0.08 g/min.

Next, an embodiment will be explained with reference to FIG. 11 wherebya plasma is used as an auxiliary energy and the location of a focalpoint of the laser beam is automatically controlled by sensing infraredrays generated from the working portion.

In the case of performing the laser working, since the energy density ofthe laser beam becomes maximum at the location of a focal point of thelaser beam, it is desirable to allow the focal point location tocoincide with the working surface. Therefore, in a conventional lasermachining apparatus, to allow a convergent point of the laser beamfocused by a focusing lens to coincide with the working surface orworking point of the workpiece, the working surface of the workpiece ismagnified by a microscope which uses the focusing lens for the laserbeam in common and is directly observed, or a sighting apparatus forobserving an image from the microscope through a television monitor isprovided and an operator operates and moves the focusing lens system soas to focus the focal point of the image.

Consequently, in a conventional laser machining apparatus, whenperforming various workings, the operator has to observe the sightingapparatus and to operate the apparatus for moving the focusing lenssystem at the start of working or during the working, whereby theefficiency is poor and a working accuracy is low.

With respect to an automatic controlling method to move the workinglaser beam in the direction perpendicular to its optical axis, i.e.,along the working surface, the automatic control can be accuratelyperformed by controlling a cross slide table for moving a workpiece oran apparatus for moving the focusing lens system for the laser beam byuse of a numerical control unit or the like. This results in an extremeimprovement in working accuracy. However, the control of movement in thedirection of the optical axis of the laser beam, i.e., in the directionperpendicular to the workpiece depends on the observation and operationby the operator. This obstructs the promotion of automation andlavor-saving for the laser machining apparatus and also obstructs theimprovement in working accuracy.

Further, for example, in a boring operation since the working portionmoves in association with the progress for working and is shifted fromthe focal point of the laser beam, the working progresses at arelatively high speed until a certain depth, but the speed thereafterbecomes slow and the working hardly progresses thereafter.

Due to this, in a conventional laser machining apparatus, the lenssystem is controlled so as to be moved in the direction of the opticalaxis of the laser beam, or the cross slide table or the like onto whicha workpiece is attached is controlled so as to be moved in the directionof the optical axis, thereby adjusting the location of the focal pointof the laser beam.

However, as mentioned above, the working portion is moved in thedirection of the optical axis as the working advances during the boringworking. Also, even during cutting, welding, quenching, etc., theworking surface of the workpiece is not always a flat planeperpendicular to the optical axis of the laser beam and the location ofthe working portion changes in the direction of the optical axis as theworkpiece is advanced; therefore, it is very difficult to move andcontrol the focal point location so as to be coincident with the workingportion. Thus, the well-known laser machining apparatus has problems inworking speed, efficiency and finishing accuracy.

To solve such problems, in the embodiment shown in FIG. 11, the locationof the focal point of the lens system is automatically controlled suchthat the maximum amount of infrared rays is always sensed from theworking point.

In FIG. 11, numeral 1101 denotes a housing; 1102 is a verticallyslidable housing attached to the housing 1101; 1103 a motor tovertically move the housing 1102 with respect to the housing 1101; 1104a laser generator; 1105 a reflecting mirror; 1106 a focusing lens; 1107a lens fixing member; 1108 a working gas supply tube; 1109 a reflectingmirror to fetch an infrared radiation generated from the workingportion; 1110 an infrared sensor; 1111 an amplifier; 1112 a control unitto control the motor 1103 in response to a signal from the amplifier;1113 a workpiece; and 1114 a plasma generating apparatus. A cross slidetable and the like to move the workpiece 1113 is omitted.

In the embodiment, the execution of boring will be described but otheroperations such as cutting, welding, quenching, etc. can be alsoperformed by a system similar to this.

The laser beam generated from the laser generator 1104 is reflected bythe reflecting mirror 1105 and is focused by the lens 1106 and isradiated onto the workpiece 1113. In the boring working, it isadvantageous to increase the energy of the laser beam per unit hour sothat a radiation energy is effectively utilized for the working in themanner such that thermal losses due to thermal conduction is made assmall as possible and the influence of working does not affectsurrounding portions. Therefore, a pulse oscillation laser or a laserwhich was pulsated by intermittently light-shielding a continuousoscillation laser is generally used.

A working gas introduced from the working gas supply tube 1108 isdischarged toward the working point through the opening at the end ofthe housing 1102. The fixing member 1107 to fix the focusing lens 1106to the housing 1102 hermetically seals the gap between the lens 1106 andthe housing 1102, thereby preventing the working gas from intruding intothe portion thereover.

A plasma jet from the plasma generating apparatus 1114 is radiated asauxiliary energy onto the opposite surface of the workpiece 1113 forimprovement in efficiency of the boring operation by the laser beam.

The focusing lens 1106 focuses the laser beam reflected by thereflecting mirror 1105 and converges it onto the working point of theworkpiece 1113, and at the same time it serves to collect infrared raysgenerated from the working point and to send them to the reflectingmirror 1109.

The housing 1102 is vertically moved along the housing 1101 inaccordance with the rotation of the motor 1103 and the focusing lens1106 is also moved together therewith, thereby adjusting a focal point.

When the laser beam focused is irradiated onto the working surface ofthe workpiece 1113, the irradiated portion absorbs the energy of thelaser beam and is heated to a high temperature, so that it is instantlyfused or evaporated and is worked. At this time, infrared rays aregenerated from the working portion which was heated to a hightemperature and the infrared energy is substantially proportional to thetemperature of the working portion.

The infrared rays from the working portion are generated almost radiallyand are collected by the lens 1106 and reflected by the reflectingmirror 1109, then they are sensed by the infrared sensor 1110.

The infrared reflecting mirror 1109 is disposed over the focusing lens1106 on an optical axis of the laser beam. Due to this, even when theworking portion is moved into the deep portion of the hole during boringthe infrared rays generated therefrom can be sensed.

The infrared sensor 1110 is attached to the outer surface of the housing1102 and is moved integrally with the housing 1102.

The infrared sensor 1110 includes an element such as HgCdTe, PbS, PbSe,InSb, PbSnTe, etc., or an element of PtSi, Ge, Hg, Au, Ga, In, etc. as atype of photo conductivity type MOSs. Such a sensor senses the amount ofinfrared rays reflected by the reflecting mirror 1109 and produces asignal responsive to its amount.

The amplifier 1111 amplifies the signal from the infrared sensor 1109and sends it to the control unit 1112.

When the signal from the amplifier 1111 is sent to the control unit1112, the control unit gives a command to the motor 1103 in accordancewith a predetermined program to make it operative, thereby allowing thehousing 1102 to be moved to the location where the output from theinfrared sensor 1110 becomes maximum.

The infrared radiation generated from the working portion becomesmaximum when the working surface is heated to a high temperature and themaximum working efficiency is obtained. Therefore, by constituting thecontrol unit 1112 so as to control the focal point location such thatthe maximum infrared energy is always detected, the focal point of thelaser beam is always allowed to substantially coincide with the locationof the working point of the workpiece. Thus, even when the working pointis moved into the inner part of the workpiece, maximum workingefficiency can be obtained.

The workpiece 1113 is attached onto an attaching base of the cross slidetable and is two-dimensionally moved in the direction of X and Y axes inthe diagram in response to commands from a control unit (not shown) suchas an numerical ccntrol unit or the like. Thus, the boring location canbe freely set and a plurality of boring workings can be continuouslyperformed.

Generally, in boring by a laser beam, when the location of a focal pointof the laser beam is largely shifted on its optical axis from the pointto be worked, its energy density becomes small, so that the workingcannot be performed. However, the working can be carried out even whenthe location of the working point is deviates from the location of thefocal point by about 1 mm.

However, the shapes of bored holes fairly differ in dependence upon thepositional relation between the working surface and the focal point.When the focal point is at the outside of the working surface, the holebecomes conical. On the other hand, when the focal point is at theinside of the working surface, the hole assumes the shape of the centralportion. In the case where the working surface and the focal pointcoincide, the hole has an almost uniform diameter and the workingefficiency becomes maximum.

Therefore, in the laser machining apparatus having the function ofautomatic adjustment for the focal point as shown in FIG. 11, during theboring the lens system is moved and controlled such that the maximumamount of infrared rays from the working point is always sensed and thefocal point of the laser beam always coincides with the working point ofthe workpiece. Therefore, the maximum working efficiency is obtained andeven when there is a variation in working depth, the working can beprogressive and a hole having an almost uniform diameter can be bored.

Next, with reference to FIGS. 12 and 13, an embodiment will be explainedwhereby a plasma jet is used as auxiliary energy and the location of afocal point of a laser beam is automatically adjusted using a lightsource for sighting.

In FIGS. 12 and 13, numeral 1201 denotes a housing; 1202 indicates ahousing attached to the housing 1201 so as to be slidable in thedirection of the Z axis in the diagram; 1203 is a motor to move thehousing 1202 in the direction of Z axis with respect to the housing1201; 1204 a laser generator; 1205 a selective transmitting mirror; 1206a window to attach the selective transmitting mirror; 1207 a focusinglens; 1208 a working gas supply tube; 1209 a working gas tank; 1210 abulkhead nozzle; 1211 a light source for sighting; 1212 a first sightinglens; 1213 a semi-transparent mirror (half mirror); 1214 a secondsighting lens; 1215 a photoelectric converter; 1215-1 to 1215-5 photosensing elements; 1216 a control unit; 1217 a workpiece; and 1218 aplasma generating apparatus. A cross slide table or the like to move theworkpiece 1217 is omitted.

The selective transmitting mirror 1205 is attached to the fixing window1206 fixed to the housing 1201 so as to form an angle of 45° against anoptical axis of a laser beam generated from the laser generator 1204.The mirror 1205 perpendicularly changes the light path of the laser beamand also transmits the sighting light which was emitted from thesighting light source 1211 and reflected by the semi-transparent mirror1213, then it sends the light toward the workpiece 1217.

In another embodiment of the selective transmitting mirror 1205, themirror may be constituted in the manner such that a micro hole is formedin a total reflecting mirror and thereby the light from the sightinglight source 1211 is transmitted through this hole.

The focusing lens 1207 attached to the housing 1202 focuses both thelight from the sighting light source 1211 transmitted through theselective transmitting mirror 1205 and the laser beam reflected by theselective transmitting mirror 1205 to the same point and converges themonto the working point on the workpiece 1217. The lens 1207 furtherreceives the light for sighting which is reflected by the workingsurface of the workpiece 1217 and returned therefrom.

The housing 1202 is attached to the housing 1201 so as to be slidable inthe direction of the Z axis. The housing 1202 is moved along the Z-axisby rotating the motor 1203, thereby adjusting the focal point of thelens 1207.

The funnel bulkhead nozzle 1210 is provided in the enlarged portion atan end of the housing 1202 and separates the portion into a radiationport 1210a for the laser beam and a working gas exhausting nozzle 1202awhich is coaxial therewith.

In accordance with the material of the workpiece 1217, a working gassuch as oxygen an inert gas, carbon dioxide etc. is supplied from theworking gas tank 1209 through the gas supply tube 1208 into a spacedportion between the housing 1202 and the bulkhead nozzle 1210. The gasis then discharged from the gas exhaust nozzle 1202a to the irradiationpoint of the laser beam.

The sighting light source 1211 is disposed at the focal point of thefirst sighting lens 1212, so that the light transmitted therethroughbecomes parallel light and is radiated onto the half mirror 1213.Although a light source which emits an ordinary incandescent light hasbeen shown as the sighting light source 1211 in the embodiment, in placeof this, a laser generator may be used which generates a laser beamhaving a wavelength different from that of the laser beam for working.In both cases as well, as the selective transmitting mirror 1205, thereis used a mirror of the type having characteristics such that the laserbeam generated from the laser generator 1204 is reflected and thesighting light is transmitted due to the difference in wavelength of thelaser beams. On the other hand, as the focusing lens 1207, there is useda lens of the type which focuses the laser beam from the laser generator1204 and the sighting light to the same point so that convergent pointsof them are not changed due to the difference in wavelength.

The semi-transparent mirror 1213 is disposed on an extended line of theoptical axis of the laser beam which is sent toward the workpiece bybeing reflected by the selective transmitting mirror 1205. Its attachingangle is set such that when the sighting light which was made parallelby the first sighting lens 1212 is reflected by this mirror 1213, theoptical axis of the reflected light coincides with the optical axis ofthe laser beam.

The semi-transparent mirror 1213 transmits the light which was reflectedby the working surface cf the workpiece 1217 and returned through thefocusing lens 1207 and selective transmitting mirror 1205, and sends thelight to the second sighting lens 1214.

Although, in this embodiment, the second sighting lens 1214 is disposedon an extending line of the optical axis of the laser beam and thesighting light source 1211 and the first sighting lens 1212 are arrangedin the direction perpendicular thereto, the positional relation betweenthem may be conversely arranged.

By arranging the optical system as described above, the optical axis ofthe parallel sighting light reflected by the half mirror 1213 is madecoincident with the optical axis of the laser beam reflected by theselective transmitting mirror 1205, then the sighting light is focusedby the focusing lens 1207 and is radiated onto the workpiece 1217. Inthis case, even if the wavelengths of the laser beam and the sightinglight differ, the convergent points of those lights can be madecoincident by appropriately selecting the material of the focusing lens1207.

The second sighting lens 1214 is also disposed on an extending line ofthe optical axis of the laser beam which is reflected by the selectivetransmitting mirror 1205. and progresses toward the workpiece. The lens1214 focuses the sighting light which had been reflected by theworkpiece 1217 and was collected by the focusing lens 1207 and isreturned by passing through the selective transmitting mirror 1205, thenit radiates the light onto the photoelectric converter 1215.

Although not shown, a protective filter may be also provided between thesecond sighting lens 1214 and the photoelectric converter 1215.

The photoelectric converter 1215 is disposed at the the focal point ofthe second sighting lens 1214 so that the distance between this lens andthe converter 1215 is fixed. The details of the photoelectric converter1215 are as shown in FIG. 13. Namely, the photo sensing elements 1215-1to 1215-5 such as photo transistors or the like are arranged in thefocal plane of the second sighting lens 1214. Such elements can sensethe sighting light which is reflected by the workpiece and passesthrough the selective transmitting mirror 1205 and semi-transparentmirror 1213 and is focused by the second lens 1214.

The photo sensing element 1215-3 is arranged at the central location ofthe focal point of the second sighting lens 1214. The photo sensingelements 1215-1 and 1215-2 and the elements 1215-4 and 1215-5 arearranged at the locations which are symmetrical around the central photosensing element 1215-3 and on the same plane as the photo sensingelement 1215-3.

Although, in this embodiment, there are five photo sensing elements1215-1 to 1215-5, the number of the elements can be freely changed inaccordance with the kinds of sighting lights or with an aperture, thefocal distance or the like of the second sighting lens 1214. Also, aplurality of such elements may be concentrically arranged around thecentral photo sensing elements 1215-3.

The signals from the respective photo sensing elements of thephotoelectric converter 1215 are interpreted and operated by the controlunit 1216. The motor 1203 to move the housing 1202 along the Z-axis iscontrolled in response to an output signal from the control unit 1216 inthe manner as described below.

Namely, when a convergent point of the laser beam by the focusing lens1207 coincides with the working plane of the workpiece 1217, aconvergent point of the sighting light also coincides with the workingplane of the workpiece 1217 and both the laser beam and the sightinglight beam focused at one point on the working plane.

The sighting light beam reflected by the working surface of theworkpiece 1217 is returned along the same light path as the transmissionpath from the semi-transparent mirror 1213 to the workpiece 1217. Whenthis sighting light beam returned is focused by the second sighting lens1214, it is focused along the light paths indicated at I and I in FIG.13 and is converged at the focal point of the second sighting lens 1214.

Since the photo sensing element 1215-3 of the photoelectric converter1215 is disposed at the focal point of the second sighting lens 1214,the sighting light beam collected at the focal point is sensed only bythe photo sensing element 1215-3, so that a strong signal is producedonly from the photo sensing element 1215-3 among the five photo sensingelements.

In this case, the control unit 1216 holds the motor 1203 in the stoppedstate, thereby maintaining the housing 1202 at a constant location.

Next, when a convergent point of the sighting light beam does notcoincide with the working surface of the workpiece, two cases areconsidered: (a) where the convergent point of the sighting light beam islocated inside of the workpiece 1217; and (b) where it is locatedoutside of the workpiece 1217.

In both cases, since the convergent points of the sighting light beamare not on the working surface, the light is radiated in a certainextended range around the working point as a center on the workingsurface and the light is reflected from this whole portion. Thus, thereflected light is not focused to one point by the second sighting lens1214, causing a light spot having an extent of a certain range to beproduced in the focal plane of the second sighting lens 1214. Forexample, it is focused along the light paths indicated at II and II inFIG. 13 and the light is sensed by the photo sensing elements 1215-2,1215-3 and 1215-4. At this time, the signal level from the photo sensingelement 1215-3 largely decreases as composed to the case where the focalpoint was correctly adjusted.

When the convergent point of the laser beam substantially deviates fromthe working surface of the workpiece, the sighting light reflected issensed by all of the photo sensing elements 1215-1 to 1215-5.

Discrimination between the above-mentioned cases (a) and (b) andcoincidence of the convergent point of the laser beam with the workingsurface of the workpiece are performed by a method which will beexplained below.

Firstly, for example, the motor 1203 is slightly rotated and the housing1202 is allowed to slightly approach the workpiece.

In the case of (a) mentioned above, the light spot formed on the workingsurface further enlarges and the light spot in the focal plane of thesecond sighting lens 1214 also further enlarges, so that the intensityof light which is sensed by the photo sensing elements 1215-2, 1215-3and 1215-4 is reduced.

In such a case, the motor 1203 is immediately reversely rotated to movethe housing 1202 away from the workpiece by a very small distance, suchthat only the photo sensing element 1215-3 receives the light.

Contrarily, in the case of (b), by allowing the housing 1202 to slightlyapproach toward the workpiece, the light spot on the working surface isreduced and the light path of the sighting light reflected approachesthe light paths I and I, causing the intensity of light which is sensedby the photo sensing element 1215-3 to be increased, so that theintensity of the signal transmitted therefrom also increases.

In such a case, the motor 1303 is further rotated in the same directionto allow the housing 1202 to approach the workpiece by a very smalldistance, thereby permitting the focused light by the second sightinglens to be sensed only by the photo sensing element 1215-3.

In this way, in both cases (a) and (b) as well, the housing 1202 ismoved by a very small distance until the focused light by the secondsighting lens is sensed only by the photo sensing element 1215-3, andthe motor 1203 is stopped when it is sensed only by the photo sensingelement 1215-3.

When the convergent point of the sighting light coincides with theworking surface of the workpiece 1217, the control unit 1216 generates acommand to radiate the working laser beam onto the workpiece.

At this time, radiation of the laser beam is controlled by increasingthe discharge electric power the power supply unit in the case where thelaser generator 1204 is a gas laser; by increasing a power of a lightemitting apparatus for pumping in case of a solid-state laser; or byopening and closing a shutter (not shown) which is provided on theoutput side of the laser generator 1204.

When the laser beam is generated from the laser generator 1204, it isreflected by the selective transmitting mirror 1205 and is focused bythe focusing lens 1207, thereafter it is radiated onto the working pointof the workpiece 1217, so that working such as boring, cutting, welding,etc. is started.

As a consequence, in the embodiment shown in FIG. 12, the focal point ofthe lens system to focus the laser beam is automatically adjusted,thereby saving labor and enabling the working accuracy to be extremelyimproved.

A part of the laser beam generated from the working laser generator canbe also utilized as a light source for sighting. In such a case, theselective transmitting mirror 1205 for reflecting the laser beam fromthe laser generator, can be constructed as a half mirror which reflectsalmost of the laser beam and transmits the other part thereof and a partof the laser beam reflected by the working surface of the workpiece isallowed to be transmitted through this half mirror and this transmittedlight is sensed by the photoelectric converter, and at the same time anaperture is provided on the output side of the laser generator and anapparatus for automatically controlling the focal point location is madeoperative by narrowing this aperture, thereafter the aperture isreleased and the working is performed.

As in the embodiment shown in FIG. 11, the infrared reflecting mirror1109 is arranged in the light path of the working laser beam. Or, as inthe embodiment shown in FIG. 12, the selective transmitting mirror 1205is used as a reflecting mirror to reflect the working laser beam to theworking portion and the sighting light is introduced to the workingportion through that mirror or is taken out from the working portion.These operations can be performed only when the auxiliary energy isradiated to a location which is slightly spaced apart from the workinglaser beam in accordance with the fundamental principle of the presentinvention. Namely, as in a conventional publicly known laser machiningapparatus, in a system which works by focusing the working laser beamand auxiliary energy to the same point, the light paths of the laserbeam and auxiliary energy complicatedly overlap, so that there is noroom where such an optical system for automatic adjustment of the focalpoint as mentioned above is interposed.

As described above, in the laser machining apparatus according to thepresent invention, a plasma jet or other auxiliary energy is radiated toa location on a workpiece which is slightly spaced apart from theirradiation point of the working laser beam. Thus, working efficiencyand working accuracy are improved and the structure of the whole systemis simplified, resulting in less failure. In addition, it is alsopossible to equip various additional apparatuses to further improveworking efficiency. Furthermore, a focal point automatic adjustingmechanism of the laser beam can be also provided.

The arrangement of the present invention is not limited to theabove-mentioned embodiments, but the invention incorporates all of thevarious changes and modifications which can be easily made by a personskilled in the art on the basis of the embodiments described in thespecification and shown in the accompanying drawings.

INDUSTRIAL APPLICABILITY

The present invention further improves working efficiency and workingaccuracy of laser machining apparatuses which are at present widely usedto work metal, glass, ceramics, plastic, or other special materials.Also, the invention is extremely useful to make the operations forworking easy and to simplify the structure of the system itself and toreduce the cost.

What is claimed is:
 1. A laser machining apparatus for performing amachining operation of a workpiece, said apparatus comprising meanssupporting a workpiece, a working laser generator for focusing a laserbeam on the workpiece to effect a machining operation thereon, anauxiliary energy generator for supplying auxiliary energy onto saidworkpiece of a magnitude to heat said workpiece without effectingmachining thereof, means for radiating said auxiliary energy onto saidworkpiece at a location spaced from the focussed laser beam forpreheating the workpiece in preparation for irradiation thereon of thefocused laser beam whereby to minimize the magnitude of laser energyrequired for machining while also minimizing thermal distortion of theworkpiece, support means supporting the laser generator and theauxiliary energy generator, means for providing relative movementbetween said support means and the means supporting the workpiece suchthat the laser beam machines the workpiece in a working progressingdirection along a determined path and means for adjusting the positionof the auxiliary energy generator relative to the laser generator incorrespondence with the relative movement of said support means and theworkpiece so that said location at which said auxiliary energy isradiated precedes the irradiation point of said laser beam in theworking progressing direction during machining of said workpiece alongsaid predetermined path.
 2. A laser machining apparatus as claimed inclaim 1, wherein said auxiliary energy is radiated to the surface of theworkpiece opposite to the surface of the workpiece onto which said laserbeam is radiated.
 3. A laser machining apparatus as claimed in claim 1,wherein said auxiliary energy is radiated to a region surrounding theirradiation point of said laser beam.
 4. A laser machining apparatus asclaimed in claim 1 wherein said means for adjusting the position of theauxiliary energy generator relative to the laser generator comprises arotatable attachment for said auxiliary energy generator around anoptical axis of said laser beam as a center.
 5. A laser machiningapparatus as claimed in claim 1, wherein said auxiliary energy generatorcomprises a plasma generating apparatus.
 6. A laser machining apparatusas claimed in claim 1, wherein said auxiliary energy generator comprisesa laser generator.
 7. A laser machining apparatus as claimed in claim 1,wherein said auxiliary energy generator comprises a glow or coronadischarge generating apparatus.
 8. A laser machining apparatus asclaimed in claim 1, wherein said auxiliary energy generator comprises anarc discharge generating apparatus.
 9. A laser machining apparatus asclaimed in claim 1, wherein said auxiliary energy generator comprises aXenon light radiating apparatus.
 10. A laser machining apparatus asclaimed in claim 6, wherein a gas discharged from said laser generatoris introduced to said plasma generating apparatus and is used as a partof plasma gas.
 11. A laser machining apparatus as claimed in claim 1,comprising means for supplying an abrasive grain to a working portion ofsaid workpiece.
 12. A laser machining apparatus as claimed in claim 1,comprising means for discharging a high-pressure working fluid to aworking portion of said workpiece.
 13. A laser machining apparatus asclaimed in claim 1, wherein a working fluid is supplied to a workingportion of the workpiece and the working is performed while evaporating80% or more of said working fluid by said laser beam and said auxiliaryenergy.
 14. A laser machining apparatus as claimed in claim 1,comprising a working fluid supplying apparatus for supplying a workingfluid to which an ultrasonic vibrational energy is applied to a workingportion of the workpiece or a portion immediately after that at whichworking is carried out.
 15. A laser machining apparatus as claimed inclaim 1, comprising a sealed casing which can enclose the workpiece anda gas consisting of a halogen or halogen compound is introduced in thecasing, and the working is carried out in said gas atmosphere.
 16. Alaser machining apparatus as claimed in claim 1, comprising a sensor tosense infrared rays generated from a working portion of the workpieceand a control unit to adjust a location of a focal point of the laserbeam in response to a signal from said sensor such that the maximumamount of infrared energy is always sensed from the working portion. 17.A laser machining apparatus as claimed in claim 1, wherein a parallelsighting light which is focused together with the laser beam at aworking portion is introduced into a light path of the laser beamthrough a selective transmitting mirror, and said sighting lightreflected by the working portion is taken out through said selectivetransmitting mirror and is focused on a photoelectric converter, and acontrol unit to adjust the location of a focal point of said laser beamby interpreting and operating an output signal from said photoelectricconverter.
 18. A laser machining apparatus as claimed in claim 1comprising support means supporting the laser generator and theauxiliary energy generator and means for providing relative movementbetween said support means and the means supporting the workpiece suchthat the laser beam machines the workpiece in a working progressingdirection along a determined path.
 19. A laser machining apparatus asclaimed in claim 18, wherein said location at which said auxiliaryenergy is radiated precedes the irradiation point of said laser beam inthe working progressing direction.